Porous pellet delay switch



Patented Jan. 28, 1947 SAT S (Granted under the act of March 3, 1883, as amended April 30, 1928; 370 O. G. 757) 3 Claims.

This invention relates to means to delay the arming of a submarine mine by a hydrostatic switch to prevent premature firing of the mine and has for its object to provide a device that will prevent the pressure acting upon such a switch from building up rapidly and so keep the mine in a safe condition for an interval after it reaches the designed depth.

With the above and other objects in view, this invention consists in the construction, combination and arrangement of parts as will be described more fully hereinafter.

In the drawing:

Fig. 1 is a longitudinal sectional view of my invention;

Fig. 2 is a wiring diagram of a circuit that includes my invention.

Fig. 2 shows the firing circuit of a submarine mine in which the battery 3 provides the electric current to fire the detonator 4 that explodes the charge of the mine. The circuit is kept open by a switch 5 that is set to be closed by the hydrostatic pressure of the water at the depth at which the mine is to be kept when planted to prevent premature explosion of the mine by accidental closing of the firing switch 6, the latter switch being designed to be closed by means actuated by contact of a vessel with suitable coacting mechanism. It is apparent that if the switch 5 is exposed freely to the pressure of the water, the mine will be armed as soon as it reaches the depth for which the switch is set. My invention prevents the arming of the mine for a predetermined interval after such depth has been attained.

Through the mine case i is passed a sleeve 8 with a widely flaring, substantially frusto-conical skirt 9 exteriorly of the case. A water-tight joint is formed by clamping the skirt against a rubber or other suitable gasket 90 by means of nuts ll screwed on sleeve 8 to bear against case I. A cup-shaped cap ['2 is screwed to the edges of 9 in inverted position with the edge of a pressure responsive diaphragm I3 clamped between the skirt 9 and a shoulder M on the cap. A sheet E5 of rubber is placed over the outer surface of diaphragm It to prevent action of the sea water upon the metal of the diaphragm and to form a water-tight seal to preclude the entry of water to the mine through the switch mechanism.

Switch stem it is slidable in sleeve 8 and carries a lug ll disposed in a slot 18 in the sleeve to prevent rotation thereof. The upper end of the stem is reduced and threaded at I9, the re- 2 duced portion being passed through the diaphragm. A rubber gasket 20 is clamped between diaphragm cover It: and the skirt of a nut 2! that is threaded on the reduced portion. The nut 2| is elongated and has a stop stud 35 screwed into the outer end thereof to fix the position of the end of the stem l5 therein. A nut 22 is screwed against the inner face of diaphragm it to clamp the diaphragm and associated parts against the nut 2|. The lower end of stem 16 is slidable in a guide 23 that is fixed to the mine case and depth adjusting spring 24 is disposed between the guide and a collar 25 fixed on the stem. One contact member 25 of the switch is carried by the lower end of stem It and the other contact 21 is carried by a fixed bracket 28.

An exteriorly threaded cylindrical sleeve 29 ex tends upwardly from cap I2 and on this sleeve is screwed a member 30 having in it a recess with threads 3| in its upper portion and a frustoconical lower portion with an aperture 32 opening into the frusto-conical portion. A gasket 33 forms a water-tight seal between member 30 and cap I 2. A bushing 34 is engaged with threads 3! and compresses packing 31 in which is seated a porous pellet 35, slightly spaced from the inner wall of bushing 34. The pellet is of porous earthenware or other suitable material through which water can pass to subject the diaphragm Hi to the pressure of the water in which the mine is planted. The cylindrical surface of pellet 35 is glazed or otherwise rendered waterproof and therefore the water must pass through the ends of the pellet and traverse the full length thereof. The time required to exert the full water pressure on the diaphragm may be controlled by varying the length, diameter and porosity of the pellet and this time can be made as short as a few seconds or as long as several minutes.

When a mine having a hydrostatic switch embodying my invention is immersed in water, the water passes through the pellet into the space around nut 21 which it fills up and then begins to exert pressure on the end of nut 2| and stud 36 and, through space 33 around nut 2|, upon diaphragm I3. This causes the diaphragm to flex downwardly and admit the water to act upon the upper surface of rubber sheet l5. After an interval the full pressure of the water at the depth to which the switch has been submerged is transmitted to the diaphragm and the spring 24 is compressed sufficiently to bring the contacts 26 and 21 together, which closes switch 5 and arms the mine. Thereafter, when switch 6 is closed by the contact of a vessel with the mechanism provided to be actuated thereby, the mine is fired, but closing of switch 6 prior to that of switch 5 will not explode the mine.

It will be understood that the above description and accompanying drawing comprehend only the general and preferred embodiment of my invention, and that various changes in construction, proportionand arrangement'of parts maybe made within the scope of the appended claims without sacrificing any of the advantages of this invention.

The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the paytneritbf 'any"ro$a'ltie's thereon or therefor.

I claim:

1. In a device of the class described, in combination, means including a diaphragm operable by fluid pressure, enclosing means for said diaphragm, a member having a 'waltertig'htconnection'with said means','said member having'in it'a cavity and'an aperture to placesaid cavity in communication with the interior of said'means, a packing element in said cavity, a porouspellet having an impermeable lateral surface and permeable end surfaces's'eated in said packing in longitudinal registry with said aperture, and a bushing around said pellet engaged in said cavity to compress said packing.

2. In a device of the class described, in combination, means including a diaphragm operable by fluid pressure, a water-tight structure substantially completely enclosing said diaphragm, said structure having through it a passage to said diaphragm, a, packing element in a portion of said passage, an elongated element seated in said packing element, said element being longitudinally permeable to water, and means disposed to protect said elongated element and compress said packing around said elongated element, said means being engaged with a portion of the wall of said passage.

3. In a device of the class described, in combination, means including a diaphragm operable by'flui'd pressure, a water-tight structure substan tially completely enclosing said diaphragm, said structure having through it a passage to said diaphragm, a packing element in a portion of said passage; water permeable means seated in said packing element adapted to prevent rapid ingress of water into said structure, and means disposed to protect said permeable means and to compress said packing around said permeable means.

ROBERT C. DUNCAN. 

